The present invention relates to a magnetic head for writing and reading data out of a magnetic disk or medium, and a magnetic disk drive playing the role of an external storage associated with a computer.
Today, many magnetic disk drives using magnetic disks as recording media use a so-called contact start and stop (CSS) type recording and reproducing system. In this type of system, while a disk drive is not operated, a magnetic head included in the disk drive rests stationary on a magnetic disk. When the disk spins at the beginning of operation, a stream of air is generated between the disk and the head and causes the head to float above the disk for writing or reading data in or out of the disk.
The distance between a magnetic body included in the disk and a recording/reproducing element included in the head floating above the disk is referred to as a magnetic spacing. Reducing the magnetic spacing, among the others, is the key to the high density recording of the disk. Recently, a magnetic spacing as small as 100 nm or below has been achieved. However, the magnetic spacing should be further reduced in order to implement the recording density of future magnetic disks. Therefore, the ultimate system is one in which the surface of the disk and the recording/reproducing element of the head contact each other in order to minimize the magnetic spacing. This kind of system is generally called a contact recording type system and attracting increasing attention as a substitute for the traditional CSS type system.
Modern magnetic disk drives are loaded with a plurality of magnetic disks in order to increase the total storage capacity. For example, a 3.5-inch disk drive promising a relatively great storage capacity is usually loaded with a stack of eight to twelve disks.
Two different measures are available for increasing the capacity of a magnetic disk drive, one which increases the recording density with which a magnetic head can record and reproduce data with a single disk, and the other which increases the total capacity of a single disk drive. Although the contact recording system is effective to increase the storage capacity for a single disk, it has some issues yet to be solved, as follows.
In the contact recording system, during recording or reproduction, the head slides on the surface of the disk while the disk spins. The disk is mounted on and driven by a rotatable spindle which forms a part of the disk drive. However, the disk involves a revolution runout component ascribable to the deviation between the recording surface of the disk and the axis of the spindle and the insufficient accuracy of the revolution surface of the spindle itself with respect to its axis. The deviation between the recording surface of the disk and the axis of the spindle is ascribable to assembly errors. Moreover, the recording surface of the disk is not fully flat or smooth, but has waving, roughness and other surface configuration components.
The revolution run-out component and surface configuration components, i.e., displacement in the direction perpendicular to the recording surface of the disk is not desirable in the contact recording type system for the following reason. When the head slides on the disk, the above displacement prevents the head from accurately following the disk and causes it to jump away from the disk. This brings about the following problems.
First, the magnetic spacing fluctuates and makes it difficult to produce a stable output during recording or reproduction, resulting in write errors or read errors. Second, the intermittent contact of the head with the disk causes the pressing load of the head acting on the disk to sharply increase for a moment. This, coupled with an impact, causes a great frictional force to act between the disk and the head for a moment while causing the disk and head to deform. Such a frictional force accelerates the wear of the disk and thereby lowers the reliability of the disk.
On the other hand, the total capacity of a single disk drive will be increased if a greater number of disks are mounted on the disk drive. However, in the conventional head and disk assembly, two heads are interposed between adjacent disks. As a result, the distance between adjacent disks cannot be reduced beyond a certain limit. It follows that the number of disks that can be mounted on a single disk drive is limited by the size of the disk drive.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 6-231555.